Unhairing of hides and skins



Patented Aug. 8, 1939 1 2,169,147 PATENT OFFICE 2,189,147 UNHAIRING OF RIDES AND SKINS Alphons 0. Jaeger, Mount Lebanon, and Richard Herrlinger, Bridgeville, Pa.,

& Chemical Corp., New York,

lean Cyanamid auilnors to Amer- N. Y a corporation of Delaware No Drawing. Application June 1, 1938.

1 Serial No. 211,182

17 Claims.

This invention relates to the unhairing of hides and skins, which is a preliminary step in their conversion into leather. An object of the invention is to provide new classes of unhairing agents which are suitable for use in neutral or alkaline .solutions or as unhairing accelerators in unhairingbaths containing lime, baths containing arsenic, baths containing pancreatin or other enzymes or any other types of unhairing baths as will subsequently be explained. A further object of the invention is to provide classes of unhairing agents or accelerators which will effect the removal of hair roots as well as hair from hides and skins without damaging the hair or'skin. A still further object of the invention is to provide classes of unhairing agents or accelerators which will contain or develop, in addition to groups having a reducing or hydrolyzing action on the keratin of the hair roots, also groups having a solvent or emulsifying action on'the fat surrounding these roots in the hair pockets.

The invention in its broader aspects will be outlined and described in terms of certain commonly accepted principles of the mechanism of unhairing. We believe that these principles are correct and that their validity is further established by the experimental evidence contained in the present specification. It should be understood, however, that the invention as exemplified by this experimental evidence is not dependent upon any theory of operation but is limited only by the scope of the claims appended hereto.

The most successful unhairing agents or accelerators now in use are lime, sodium sulfide and red arsenic (AS283). It is generally considered that the efiiciency of these materials is due either to a reducing action or a hydrolyzing action, or both, on the disulfide linkages of the keratinous proteins of the hairs and hair roots. This theory was announced by H. B. Merrill in Chem. vol. 17, page 36 (1925).

'An unhairing agent of the type of sodium sulfide, while rapid and effective, attacks the hair above the point where it enters the hair pocket. The result of this action is that the hairis weakened and breaks oil above the surface of the hide; leaving the hair root embedded in the hide or skin from which it can be extracted only with diiliculty.

Our investigations have shown that the failure of'such unhairing agents or unhairing accelerators as sodium sulfide to remove the hair roots is due to a lack of penetration of the unhairing agent into the hair pockets containing these hair roots rather than to any lack of chemical action, for the hair roots consist of the same material as the hair itself.

In order to remove the hair roots without harming the hide or hair, and to produce a fine and clean grain, the unhairing agent or accelerator J. Ind. Eng.

bulb can slip from its sheath, leaving the hair pockets clean and open for the following scudding and hating operations. Unhairing agents which are strong alkalies have great difilculty in doing this because of the presence in these pockets of the fat provided by nature for protection and lubrication of the hair roots.

Lime, sodium sulfide and sodium hydroxide, which are the conventional unhairing agents, would in time saponify the fat in the hair pockets but the resulting soaps are bulky and tend to plug any available opening. At the same time the strong alkalinity of these agents hinders the removal of the hair by swelling the skin until the openings of the hair pockets are constricted, so that the thicker hair bulbs cannot get out and the alkali cannot enter.

For the above reasons the conventional alkaline unhairing agents are slow in action and must be used in such high concentrations that the hair is attacked. Most of its breaks off at its weakest part just above the hair bulb, leaving the hair bulbs embedded in the grain of the leather.

By a study of the above limitations in known unhairing agents and unhairing accelerators we have arrived at the principles of the present invention, which may be stated briefly, as follows:

(1) An unhairing agent or unhairing accelerator capable of liberating the hair roots must contain or develop in the unhairing bath one or more groups capable of disrupting the disulfide linkages of the'keratinous matter surrounding the hair roots. This disruption is due to a chemical reduction and/or hydrolysis of these linkages by the unhairing agent, as stated' by Merrill in the publication above referred to.' Such reducing and/or hydrolyzing groups are usually polar in character.

(2) The unhairing agent or accelerator must contain or develop under unhairing conditions one or more fat-solvent groups; that is to say, groups which will have a solvent, emulsifying or penetrating action on the layer of fat surrounding the hair roots. Such fat-solvent groups are usually non-polar in character.

(3) The reagent should not be too alkaline; it should not develop during unhairing a pH such that alkali swelling becomes objectionable. In the following specification and claims, we shall use the term non-swelling to designate this characteristic. a r

(4) It should preferably have a relatively low molecular weight in order to facilitate penetration into the hair pockets, but this is not an absoand/or hydrolyzing group must be in chemical combination; 1. e., they must be contained in the same molecule. We have tested the action of mixtures of sodium sulfide with acetone and similar mixtures of fat-solvent with known unhairing agents. It all cases the mixture was no better than the unhairing agent when used by itself.

(6) The unhairing agent or accelerator should be at least slightly water soluble or water-dispersible, for obvious reasons.

We have found that any compound which fulfills the above conditions will be a good unhairing agent. We have tested out a number of classes of compounds containing polar-non-polar groups that seemed to satisfy the above requirements and in every case we found that all members of the class in question were operative. Naturally, some members of any given class were found to be more efilcient than others, but any inferiority could always be traced to some deficiency in fulfilling one or more of the requisite conditions.

The above analysis has enabled us to identify entire classes of unhairing agents capable of liberating hair roots by an inspection of their type formula or by simple tests to determine if they contain groups of the necessary characteristics. Accordingly, we regard our invention in its broader aspects as including the use as an unhairing agent or unhairing accelerator of any compound or class of compounds that fulfills the above requirements.

In some of its more limited and preferred aspects our invention deals with certain classes of compounds which meet the above requirements of a satisfactory unhairing agent or accelerator and which we have found to be unusually effective for accomplishing the objects of the invention. We will describe and discuss the characistics of a. number of such classes of compounds and illustrate their use in the following specific examples, but it should be understood that these examples are given primarily for the purpose of illustrating the invention as a whole and that our inventive concept is limited to their subject matter only in certain of the more limited claims appended hereto.

(a) Xanthates This class of compounds is perhaps the best of all that we have tried, for all the relatively large number of xanthates which we have used appear to have a uniformly good unhairing action. Some of the higher alkyl xanthates such as the xanthates of dextrose, sucrose, and the like are not quite as efficient as are the lower xanthates by reason of their higher molecular weight but aside from this limiting factor the xanthates as a class comply with all the requirements of the present invention.

The xanthates have the following type formula:

OAlk

BMe

in'which Alk may be a primary, secondary or even a tertiary alkyl radical and Me is a positive group capable of forming a salt with the xanthate such as sodium, potassium, calcium, ammonium or any other alkali or alkaline earth metal or basic groups such as methylamine, dimethylamine, guanidine, etc. They are prepared according to known methods by the interaction of carbon bisulfide and alkali metal hydroxides in an excess of an alcohol corresponding to the desired alkyl radical, or by reacting a carbonate or other salt of the desired basic group, for example guanidlne carbonate, with a mixture of the alcohol and carbon bisulfide in the presence of barium hydroxide.

It is evident from the association of groups contained in this class of compounds that its nucleus will have a. strong afilnity for fat and will readily penetrate the fat of the hair pockets. It is also evident that the compound will have both a reducing and hydrolyzing action on the disulfide linkages of thekeratinous hairroots for it contains the group -SMe which is known to have such an action. The xanthates as a class are neutral or only slightly alkaline, they are water-soluble, and of relatively low molecular weight. Accordingly, they fulfill all the conditions necessary for a successful unhairing agent capable of liberating hair at its roots in accordance with the present invention.

(b) Esters of thiocarbamic acid These compounds have the type formula:

Nam, where A is alkyl, aryl, aralkyl, terpenyl, or in general any radical derived from an alcohol or phenol, and R1 and R2 are hydrogen or other positive groups capable of forming a substituted amide. In this class of compounds the group 0A I o=s is a fat-solvent or fat-emulsifying group and aids in the-penetration of the compound into the hair pockets, while the group -NR1R2 is a hydrolyzing agent of the type of dimethylamine, which is known to be an unhairing agent.

(0) Salts and esters of dithiocarbamie acid These compounds have the type formula:

in which Pos represents a positive group capable of forming a salt or an ester with the compound, such as alkoxy, aryloxy or a metal such as sodium, potassium, or other salt-forming group such as ammonium, etc., and R1 and R2 are hydrogen or other positive groups capable of forming a substituted amide. This class of compounds contains as a hydrolyzing group the amido or substituted amido group and also in the case where P05 is a salt-forming group they contain groups which are analogues of sodium sulfide. The compound has fat-solvent or fat-emulsifying properties by reason of the group.

so:s

which resembles carbon bisulfide in its fat-solvent properties.

(d) Salts of trithiocarbonic acid The type formula for this class of compounds is as follows:

where Me is a positive salt-forming group. It is evident that the compounds of this class have both fat-solvent, reducing and hydrolyzing properties since they contain groups of the Mes type as well as a group (e) Salts of tetrathiocarbonic acid The formula for this class 0t compounds is as follows:

(I) Salts and esters of thiolcarbamic 'acid These compounds have the type formula: 5 Pos v Nmm where the symbols have the same relative significance as in (c). In this class of compounds the amide group provides the reducing and hydrolyzing action and an affinity for fat is created by the COS- group.

(g) Ester salts of thiocarbonic acid These compounds have the type formula:

S.Me where A is as previously defined, and Me is a positive, salt-forming group. Here, as in several of the compounds previously discussed, the group S.Me is a reducing and hydrolyzlng group while the ester group creates an afllnity for fat.

The similarity of the principles of operation of the above and similar classes of unhairing .agents and accelerators to the modern theory of wetting agents may be helpful in explaining the advantages of the invention. It is well known that a good wetting agent causes water to wet an oily surface'because it contains. in the same molecule, hydrophile groups which have an aflinity for water and hydrophobe groups which have an afilnity for oil. Similarly the unhairing agents of the present invention, as has been demonstrated, contain groups which have an afiinity for, and therefore a solvent action upon, the layer of fat surrounding the hair roots., These groups, therefore, facilitate the penetration of the un-- hairing agent into the hair pockets and aid in bringing the entire molecule into contact with the keratin of the hair roots. When this has been accomplished the reducing and/or hydrolyzing groups of the molecule are capable of directly attacking the disulfide' linkages of the keratinous materials surrounding the hair roots 05 and opening up the molecule for further attack by the lime or other hydrolyzing agent which may also be present in the bath.

METHODS OF APPLICATION The unhairing agents or accelerators of the 70 invention may be applied to the hides or skins by any known or approved method. Thus, for example, they may be incorporated in an unhair ing bath of lime in which the hide is immersed or they may be applied in the form of a depila- 75 tory paste such as is frequently used in unhairing sheepskins. Inaddition to their use asthe chief unhairing agent we have also found that they are excellent unhairing accelerators for alkaline unhairing agents such as lime and sodium carbonateand that they may be used to advantage in admixture with known unhairing agents such as red arsenic or sodium sulfide; with reducing agents such as sodium hydrosulflte; and with proteolytic enzymes such as pancreatin.

The xanthates'and other depilatories of the invention may be used in admixture with the above described materials or as a separate treatment preceding or following their use, or both. For example they may be used for extracting hair roots from stock which has been unhaired by other processes which leave some or all of the hair roots intact. This is'sometimes done purposely in the manufacture of patent leather by treating light stock with a strong bath containing sodium sulfide to dissolve or weaken the hair and cause it to break of! at the surface of the skin. The stock may then be treated with a bath containing one or more of the unhairing agents of the present invention in order to loosen the hair roots.

Unhairing baths or pastes containing the unhairing agents of the present invention may also contain auxiliary materials such as wetting agents, penetrating agents, emulsifying agents, softening agents and the like. An example of such an auxiliary material is the sodium salt of isopropyl naphthalene sulfonate, which is a well known wetting and penetrating agent.

The invention will be illustrated by the following specific examples, which show representative unhairing agents or accelerators included therein and representative methods of application. It should be understood, however, that these examples are given primarily by way of illustration and that the invention in its broader aspects is limited only by the claims appended hereto.

EXAMPLE 1 Procedure a. Steer hide.Domestic wet-salted steer hides were weighed and washed in running water for one-half hour, soaked' overnight, and again washed for one-half hour in a drum. I The hides were then suspended in four times their weight of lime solution containing an amount of lime equal to 8% of the weight of the hides before soaking and .an amount of xanthate or other accelerator as indicated in this and other examples. The hides were agitated for about one-half minute every hour during several hours on the first and on the second day, and tested for hair looseness after 8, 24 and 48 hours.

b. Goatskins.Dried goatskins were weighed and soaked for two days changing the soaking water once every day, then washed in running water for thirty minutes. The skins were then suspended in four times their weight of lime solution containing an amount of lime equal to 20% of the weight of the skins before soaking and an amount of accelerator as indicated.

In most cases the unhairing agents were tested in various concentrations. The percentage given in the following tables is the lowest quantity which gave the results indicated. These percentages are based on the weight of the hides before soaking.

Terms used The following terms have been adopted for the sake of simplicity and will be used in this and subsequent examples. The values represent the average results obtained by an experienced observer from several tests.

1. Unhairing acceleration.-

Excellent: On steer hide the hair comes of! easily after 24 hours orless with practically no fine hair remaining when the skin is pressed with a dull unhairing knife in the direction of the Summary of results 1 Condition 01- Accclcrator g figg g Percent Odor oi lime Hair Skin Sodium methyl xanthate Excellent... .5 A A g 3, Potassium ethyl xanthate d 5 A A D() Sodium ethyl xanthate b A A Do. Sodium isopropyl xanthate. 6 A A Do. Potassium sec. butyl xanthate .5 A A D Ximthate oi glycol 5 A A Notic. H18 and S. Xanthate oi glycennc l. .5 A A Do, Xanthate of glucose 1. 5 A A Do, Xanthate of sucrose 6 A A Do. Xanthate oi molasses. 1 A B brown Do. Xnnthate of hydrogenated sugar 1 A A Do. Xanthato of aminated sugar 1 A A Do. Xanthate oi methylamine sugar l A B brown Do. Xanthate of starch 1 A A Do. Xenthate of eellulos l A B 1) Sodium sulllde.. 1 0-D. B 0 Nutic. lhS Dimethylsmine. 1 A A llnd. Lime alone 1 A A Si. Amm

hair. After 48 hours the hair, including all fine hair, comes off very easily when the hide is simply rubbed with the finger. On goatskins, the same results are obtained after 48 hours and 62 hours respectively.

Very good: On steer hide the hair comes ofl with an unhairing knife after 24 hours, but some fine hair remains which after 48 hours can also be removed by using an unhairing knife with slight pressure. All the fine hair cannot be removed using finger pressure alone. For goatskins these times are 48 hours and 72 hours respectively.

Good: The hair is not sufficiently loose after 24 hours but can be satisfactorily unhaired after 48 hours for steer hide and 72 hours for goatskins, using medium pressure on the unhairing knife.

Fair: The hair is insufficiently loose after 48 hours for steer hide and '72 hours for goatskins,

but considerably better than with pure lime solutions.

Poor: The hair looseness is no better than with lime alone.

2. PZumping.-The terms much", "little" and none" are self-explanatory.

3. Condition of hair.--The hair after 48 hours unhairing was examined with a magnifying glass for the presence of hair roots and for signs of attack. It was tested for strength by pulling it apart with the fingers.

A. Excellent; Strong hair with roots intact.

B. Strong hair but with roots broken off.

C. Weak, hair attacked.

D. Hair destroyed.

4. Condition of skim-The skin after unhairing and scudding was examined for clearness, smoothness of grain and for discoloration.

The above results show that the xanthates derived from monohydric alcohols are more effective as unhairing accelerators than those of polyhydric alcohols, which are in turn better than those derived from sugars. They also show that the effectiveness of the accelerator decreases with increasing molecular weight. Sucrose xanthate is apparently an exception to this rule, since it is better than the xanthates of glycol and glycerine.

It will be noted that all the xanth'ates as a class produce hair of excellent quality with the hair roots still attached after unhairing. The skin was in all cases clean, white and -of good grain except when using the xanthates 01! molasses and methylaminated sugar. All the min- 'thates produce a degree of plumpness classified as little; the skin is less plump than with sodium sulfide but a little more plump than with dimethylamine.

Sodium sulfide, dimethylamine and lime alone were tested simultaneously with the xanthates for purposes of comparison and the results are given in the table. It will be noted that sodium sulfide attacks both the hair and the skin, and while the ease of unhairing after 24 and 48 hours was rated as excellent" an examination of the hides after unhairing showed that most of the hair roots were still embedded in them. Dimethylamine, while a good unhairing accelerator, develops a bad odor.

Exlmru: 2

This example illustrates the use of esters of thioca'rbamic acid, salts and esters of dithloimproved.

as lime. The tests were made on steer and goatskins using the same procedure and type of lime bath as in Example 1, and the same terminology sible, painted uniformly on the flesh side with the depilatory paste, folded together flesh against flesh and tested for hair looseness after 8, l8 and not as effective accelerators as their isomers, the thiolcarbamates, in which the sulfur is present in the form of the-group These latter compounds, especially in the form of their dimethylamine salts, are as efieotive as the best of the xanthates. Their reduction products containing a -C-SC linkage, such as thiuram monosulfide, also gaye good unhairing acceleration. 1

The thiocarbonates also showed very powerful unhairing action, being about equal in this respect to sodium ethyl xanthate. There was no noticeable difference between the potassium and ammonium salts of trithiocarbonate and tetrathiocarbonate.

The action of these unhalring agents on the hair and skin was uniformly mild. Some of the tests were duplicated with the addition of 0.5% and 1.0% of such wetting agents as sodium dioctyl sulfosuccinate and isopropyl naphthalene sodium sulfonate. In these cases a cleaner skin was obtained, but the accelerating action was not greatly EXAIIIPLI 3 This example illustrates the use of the unhairing agents of the invention in depilatory pastes for use onsheep skins.

A standard depilatory'paste consists ofhydrated llme, unhairing accelerator and water. Equal volstiffness.

Procedure Domestic long-wool sheep skins were washed in a drum for one-half hour and soaked overnight at 15 C. The skins were then pressed by hand to remove as much of the surface water as posisused in expressing the results. 24 hours.

' Summary of results o i I U m Condition of- Aooelerator gm' g Percent Odor of lime 1 Hair Skin Eth '1 thiocarbamate 1 A a '7 A N. l 'dlmethylthiourethane... i A A Bl D o? Ammonium thiolcarbamate. Very good. i A A Notic. H 5. N, lf'dimletthylthiolcarbamic acid dimethyla- Excellent 0. 6 A A S]. Amm.

m ne se Ammonium dithioearbamato 0, 5 A A N u Hag,

I N, lildimfithyl dithiooarbamic acid dimethy-' 0. 5 A A 888? m no so Thiuram monnsuliide o 5 A g a 'Ietramethyl thluram monosulilde 0. 5 A i 8:. s Ethyl potassium monothiocarbonate. 0. 5 A A Notio. H S. 'lrithio ammonium carbonate 0. 5 A A Do. Potassium trithiocurbonate. 0.5 A A Do. Potassium tetmthiocnrhonate. 0.5 A A Do. Sodium sulfide. 1 0-D B-O Notio. H S. Dimethylamine l A A Bad. Lime alone 1 A A 81. Am.

These results show that the thiourethanes are Results The following formulas gave as good unhairing 'as 15% sodium sulfide after 8 hours:

" 10% sodium ethyl xanthate+2% NaOI-I 10% sodium ethyl xanthate+l% NaOH+1% red arsenic 1 5% sodium ethyl xanthate+2% NaOH+2% Nazszoi After 24 hours sodium ethyl xanthate alone gave excellent results in concentrations as low as 3%, while the potassium trithlooarbonate and xanthate of sucrose in concentrations of 540% save as good results as sodium sulfide. In all cases the appearance of the skin was better when the xanthates and trithiocarbonate were used than with sodium sulfide and the wool was less attacked; Exaurer: 4

This example illustrates the use of the unhairing agents of the present invention in conjunction with other unhairing agents. In many cases the mild action of our unhairing agents will permit their use in admixture with cheaper and less satisfactory materials while still retaining at least some of the advantages of the invention.

The tests were made on goatskins. and steer hide using the procedure and type of lime bath outlined in Example 1. However, the effect of variations of temperature in the unhairlng bath was also noted. All percentages are based on the soak-weight of the hides or skins; that is to say, their weight before soaking.

Table of results Sodium Unhairin ethyl 2. 3g" NaOH Temp. 8 xanthate Steer Goat Percent Parent Percent F.

1 70 EXCQHBDL'... Verygood.

70 Fair Fair. 70 70 70 Do. 70 do Verygood. 70 Very good... G 70 Excellent... Ver good. 70 0. 85 ....c.o .4 Do. 85 -..co Do. 85 c Do.

70 Very ood. 70 Excel out. 85 Do. 85 Do. 85 Good.

With 1% sulfide the hair was weak after 48 hours both on the steer and on the goatskins and the skin appeared stained. With 0.75% the skin was slightly stained, but the hair was strong. All other combinations gave strong hair and a clean skin.

The goatskin pieces used in these tests were not easy to unhair. While fine differences could not be detected between some of the variations used, it was very evident that the addition of sodium sulfide, sodium hydroxide and red arsenic considerably increased the unhairing action of sodium xanthate and made it possible to reduce the amount of the latter and obtain the same results. Increase of temperature also accelerated the unhairing action markedly. A combination eifect seems to be best. The best results were obtained with .30% xanthate, .20% red arsenic, .2% sodium hydroxide at 85 F. Red arsenic was more effective than sodium sulfide. The

much better results than either of these agents alone. The combination 30% xanthate and 20% hydrosulflte gave the best unhairing, a clean skin and strong hair. Addition of sodium hydroxide was also beneficial, the most effective being .30% xanthate, 20% hydrosulflte and .2% sodium hydroxide.

Additional tests were made on goatskins and steer hides to show the effect on unhairing of additions of red arsenic (ASzSz) and of varying amounts of sodium hydroxide. It was found that the combination of 0.5% sodium ethyl xanthate, 0.5% sodium hydrosulfite and 0.25% red arsenic in a lime bath containing 0.5% NaOH, all based on the soak-weight oi' the hides, gave the best unhairing after 24 hours, but that this combination attacked the hair after 48 hours.

The following table shows that larger amounts of xanthate and hydrosulfite will improve the unhairing during the first 24 hours, but that after Table of results Unhamng Condition alter Mixtures Plumping 48 48 hrs.

24 hrs. 48 hrs. Skin Hair .3 xanthete .2 hydrosulflte Good .Exoellent.. Little. A A .5 xanthute .2 hydrosulilte "do ...do do A A .5 xunthute .5 hydrosuliite Good to exoellent.. .do Much..... A A .5 xunthate.5hydrosu1flte ..do .do ..do A A .25 red arsenic W7 NaOH lxanthate.25 red .do A A arsenic 34% NaH. .3 xunthnto .2 hydrosulflte--.l NaOH Very good ...do. Little. A A .3 xunthnte .2 hydrosuiflte.2 a NaOH (1 .d0 .do A A .3 xuuthate.2.hydrosulil to.b7 NaOH..... A A .3 mutilate-.25 red arsenic .2% e011 ttle A A .3 xanthate-.25 rod arsenic .6% NaOH A A higher temperature and .2% NaOH gave also the best result in the sodium sulfide series.

All pieces where sodium hydroxide had been added were noticeably plumper than the others but none was excessively plump.

EXAMPLE 5 Good results are also obtained when the unhairing agents of the present invention are used in conjunction with sodium hydrosulflte, with or without the addition of alkalies such as sodium hydroxide. The procedure used and type of lime bath was identical with that described in Example 1.

Table of results 48 hours the results are about the same whether larger or smaller amounts are used.

With 0.5% sodium hydroxide the skins plumped too much and did not unhair as well as with less. There was little difference between 0.1 and 0.2% of sodium hydroxide. Apparently it is best to add enough caustic soda to obtain the highest degree of alkalinity without excessively plumping the hides or skins, and this amount may vary greatly depending on the amount of lime, agitation and type of skin used.

Exliupu: 6

The unhairing agents of the present invention Results Condition of Sodylufn Hydro N H after 48 hours P M at y e um ng xanthate Steer Goat Skin Hair Percent Percent Percent i Excellent Verygood. A D Much.

A C Do. i 2 Little.

0. A A Do.

A A None. .40 .10 A A Little. .30 .20 A A Do. .20 .30 A A Much. i0 l0 2 A A D0. .30 .20 .2 A A Do. 1 .2 A A Do. .50 2 A A Little. .30 .20 1 Excellent..." A A Much. .30 .20 3 Very good A 0 Do.

Sodium hydrosulfite had a very good unhairing action and. produced a clean skin, but it attacked the hair when used in concentrations high enough for effective unhairing. Sodium xanthate in concentrations as high as 1% did not attack the hair.

The mixtures of xanthate and hydrosulfite gave may also be used in unhairing processes employing proteolytic enzymes such as pancreatin, and papain. When so used they produce a cleaner and finer grain and increase the efllciency of the unhairing process.

Tests were made on steer hides using the procedure and type of lime bath described in Exzyme preparations were first suspended in a small amount of water and then added to the lime liquors containing the accelerators.

Table of results I Accelerator combination Unhairing i .g;xsn t l iags .fi xan ae-. pancrean er .aei. minibus-52% AszS|+-l7 NaO Exc l cnt. 3% xanthste-l-.2% As:S|+.l NaOH+.2% pnncroatin Do. .3? xanthata- Na:8i0|+.l% NsOH Do. .3 xauthate-h o NaeSi0i+.i% Na0H+.2% psn- Do.

cros n.

Tests of sodium ethyl xanthate were also made in solutions containing sodium carbonate and ammonium chloride, but no lime, adjusted to a pH between 8 and 9 and a'temperature of C.

0.5% of the xanthate and 0.2% of Pancreatin were added to these solutions and the unhairing action wasnoted. It was rated as very good.

Exams: 7 Another field of application of the unhairing agents of the present invention is their use prior to or subsequent to other unhairing accelerators. For example, it is possible to avoid the severe action of such accelerators as sodium sulfide and sodium hydrosulfite on the hair and grain of the skins by immersing them for only a short time in limes containing these materials and then finish ing the unhairing in a lime bath containing a xanthate, an ester or salt of dithiocarbamic acid, or any of the other unhairing agents or accelerators which we have described as being included within the scope of the invention.

Unhairing tests were made on steer hide according to this procedure using the methods outlined in Example 1 with 8% lime and 400% water in both unhairing baths except in the bath containing sodium carbonate and ammonium chloride, where no lime was used.

" .Tableof results in conjunction with the xanthate and the other agents than when used either prior. to or following these agents.

In the foregoing examples various methods of application of our unhairing agents havebeen illustrated. The first two examples illustrate the action of a number of xanthates and other dc.- rivatives of carbon 'bisulflde in simple lime solutionswhile the remaining examples are intended to show how many oi these substances may be employed in other fields of application. Accordingly it should be understood that whenever a xanthate or any other specific unhairing agent of the present invention is specified in these latter examples it is intended to be illustrative of the compounds :de'scribed in Examples 1 and 2,

and that any of the compounds specified in Examples 1 and 2 can be substituted for those used in the subsequent examples.

What we claim is: LA method of unhairing hides and skins which comprises contacting them for a sufilcient period of time with an unhairing composition comprising an aqueous dispersion of a non-swelling compound containing in chemical combina-.

tion at least one group capable of disrupting the disulfide linkages of keratin and at least one fatsolvent group containing an atom of carbon which comprises contacting them for a sufiicient period of time with an unhairing composition comprising an aqueous dispersion of a nonswelling compound containing in chemical com- Unhairing 1 bath Hrs. 11 bath mf- 2ihrs. 48 hrs.

1 ,sodium sulfide '8 .5 sodiumethylxanthate Excellent... B. 1 sodium herdrosulfite 8 .6 sodiumetbylxanthste .do B. l 0 red arson c 8 5%sodium cthylxanthate A. 1 sodium sulfide. 48 C. i 0 sodium hydrosulfi 48 do..... I). red arsenic +25 NaOH. 24 .3% sodium ethyl xsnthate Very ood A; Pineall tarsenic-{=25 NaOH+.3% 48 Excel out... A.

ran as.

hydrosulfiie+.25 NaOH 24 3% sodium ethyl xanthate Good A. htyldrosulfiteifl Na.0 H+.3% 24 Excellent... A.

no a e. 2% hgd{osulfitc+.25 Na0H+.3% 24 3% pancrcatin Very good". A.

rant 1! e. 2% hydrosuliito. 25% NaOH, .3% 48 Excellent... A. xanthatc, .3% pancrestin. .3% ancreatin, Na CO;+BN Cl M .2% hydrosulflte, Good A.

(pIPS.5). 1 NaOH, .3% xanthate.

Sodium hydrosulfite and sodium sulfide alone attacked the hair very seriously after 24 and 48 hours unhairing. The hair was not attacked, or only slightly so, when the treatment with these agents was short and followed by a final unhairing with sodium xanthate. Separate pretreatment with small quantities of sodium hydrosulfite, red arsenic and caustic soda, followed by a treatment with xanthate. did not give as good results as when. these agents were all together from the start. I

Pancreatin also gave better results when used bination at least one group capable of disrupting the disulflde linkages of keratin and at least one fat-solvent group containing an atom of. carbon directly linked to two atoms of sulfur.

4. A method of unhairing hides and skins which comprises contacting them for a sufilcient period of time with an unhairing composition comprising an aqueous dispersion of a nonswelling compound containingin chemical combination at least one group capable of disrupting the disulfide linkages of keratin and at leastone fat-solvent group containing an atom of carbon directly linked to an atom of sulfur and also directly linked to an atom of oxygen.

5. A method of unhalring hides and skins which comprises contacting them for a sufiicient period of time with an unhalring composition comprising an aqueous dispersion of a non- 7. A method of unhalring hides and skins which comprises contacting them for asufiicient period of time with an unhalring composition comprising an aqueous dispersion of a compound selected from the group consisting of ester salts of thiocarbamic acid and salts of trithioand tetrathiocarbamic acids.

8. A method of unhalring hides and skins which comprises contacting them for a sufficient period of time with an unhalring composition comprising an aqueous dispersion of a compound selected from the group consisting of salts and ester salts of thiolcarbamic acid.

9. A depilatory composition comprising an alkaline hydrolyzing agent and a. non-swelling compound containing in chemical combination agroup capable of disrupting the disulflde linkages of keratin and a fat-solvent group containing an atom of carbon directly linked to an atom of sulfur.

10. A depilatory composition comprising an alkaline hydrolyzing agent and a non-swelling compound containing in chemical combination a group capable oi disrupting the disulflde-linkages of keratin and a fat-solvent group containing an atom of carbon doubly linked to an atom of sulfur.

11. A depilatory composition comprising an alkaline hydrolyzing agent and non-swelling compound containing in chemical combination a group capable of disrupting the disulfide linkages of keratin and a rat-solvent group containing an atom of carbon directly linked to two atoms of sulfur.

12. A depilatory composition comprising an alkaline hydrolyzing agent and a non-swelling compound containing in chemical combination a group capable of disrupting the disulfide linkages of keratin and a fat-solvent group containing an atom of carbon directly linked to an atom of sulfur and also directly linked to an atom of oxygen.

13. A method of unhalring hides and skins which comprises contacting them for a sufllcient period of time with an unhalring composition comprising an aqueous dispersion of a. compound having the formula Z- Pos in which Z is a member of the group consisting of sulfur and oxygen, Pos is a member of the class consisting of salt-forming and ester-forming groups, and X is a member of the known class of keratin-splitting groups consisting of S-Me and NRiRz, in which Me is a salt-forming group and R1 and R2 are hydrogen or positive groups capable of forming a substituted amide.

14. A method of unhalring hides and skins which comprises contacting them for a sufficient period of time with an unhairing composition comprising an alkaline hydrolyzing agent and an aqueous dispersion of a compound having the formula Z-Pos in which Z is a member of the group consistin of sulfur and oxygen, Pos is a member of the class consist ng of salt-forming and ester-forming groups, and X is a member of the known class of keratin-splitting groups consisting of SMe and NRIRZ, in which Me is a salt-forming group and R1 and R2 are hydrogen or positive groups capable of forming a substituted amide.

15. A method of unhalring hides and skins which comprises contacting them for a sufficient.

period of time with a lime suspension which also contains an aqueous dispersion of a compound having the formula Z-Pos in which Z is a member of the group consisting of sulfur and oxygen, Pos is a member of the class consisting of salt-forming and ester-forming groups, and X is a member of the known class of keratin-splitting groups consisting of S-Me and NRiRZ, in which Me is a salt-forming group, and R1 and R2 are hydrogen or positive groups capable of forming a substituted amide.

16. A method of unhalring hides and skins which comprises contacting them for a suflicient period of time with an unhalring composition comprising an a kaline hydrolyzing agent, a compound having the formula in which Z is a member of the group consisting of sulfur and oxygen, Pos is a member of the class consisting of salt-forming and ester-forming groups, and X is a member of the known class of keratin-splitting groups consisting of S-Me and NRIRZ, in which Me is a salt-forming group and R1 and R2 are hydrogen or positive groups capable of forming a substituted amide, and another unhairing agent.

17. A depilatory composition comprising an alkaline hydrolyzing agent and a compound having the formula Z-Pos in which Z is a member of the group consisting -of sulfur and oxygen, P05 is a member of the class ALPHONS O. JAEGER. RICHARD HERRLINGER.

' Patent No. 2,169,1h7.

CERTIFICATE OF CORRECTION.

I A t 8, 959. ALPHONS o. JAEGER, ET AL.

It is hereby certified'that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 1, sec' 0nd column, line 25, for the word "its" first occurrence read it page '5, first column, line 16, in the table, for "dimethymine" read dimethylamine;

page 6, second column, line 50, in the table, last column thereof, under the sub-heading .Hair" for "A" read B; line 51 in the table, last column thereof, for "Plumbing" read Plumping; page 7, first column, line 15, third last line of the table, for "2%" read .2%; line 61, in the table, for "HNuCl" read NH Gl; and second column, line 10, for "many" read any; page 8, first vcolumn, line 26, claim 7, for "thiocarhamic" read thiocarbonic; line 27, same claim, for "tetrathiocarbamic" read tetrathiocarbonic; and second column, line 67, claim 17, for "E-He" reads-Me; and that the said Letters Patent should be read with this correction therein that the same ,may conform to the record of the case in the Patent Office.

Signed and sealed this 26th day of September, A. D. 1959.

Henry ,Van Arsdale, (Seal) 7 Acting Commissioner of Patents. 

